| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2005: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
Melanocortins including α-, β-and y-melanocyte stimulating hormone (MSH), and adrenocorticotropin exert a number of biological functions through melanocortin receptors (MCRs). We studied melanocortin system in rats and mice. Rat proopiomelanocortin (POMC) gene promoter activity was analyzed using luciferase reporter gene. We examined whether Tpit/PitxRE and NurRE are involved in CRH/cAMP-induced activation and glucocorticoid (Gc)-induced repression of POMC gene expression. Deletion and mutation of Tpit/PitxRE markedly reduced basal activity of the promoter, and those of NurRE decreased the levels of the CRH/cAMP-induced activation. Nifedipine, KN-62, and W-7, specific inhibitors of the L-type calcium channel, calmodulin-dependent protein kinase II, and calmodulin respectively, attenuated CRH/cAMP-induced activation of promoters with 3 copies of either Tpit/PitxRE or NurRE, indicating that both Tpit/PitxRE and NurRE mediate CRH-induced activation of POMC gene expression in a calcium dep
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endent manner. Deletion and mutation of Tpit/PitxRE abolished dexamethasone (DEX)-induced repression of POMC gene expression, while those of NurRE did not, indicating that Tpit/PitxRE predominantly mediates Gc-induced repression of POMC transcription.
Five subtypes of MCRs (MC1R to MC5R) have been reported and expressed in various tissues. MC3R have been reported to be involved in the regulation of feeding behavior and prolactin secretion. The present study was aimed at clarifying the regulatory mechanism of mouse MC3R gene expression. We studied mouse MC3R gene promoter activity using luciferase reporter gene. The transcription initiation site was localized at-457 bP from the translation start site. The promoter activity of the 5'-flanking regions of MC3R gene was studied using HEK 293 cell, GH3 cells and MCF-7 cells. Deletion analysis of the 5'-flanking regions of MC3R gene was performed to clarify the promoter of MC3R gene. We found that the sequence from-1284 to-524 contains positively acting regulatory elements, while the sequence from-524 to-227 negatively acting regulatory elements. Less
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